Comet Shoemaker-Levy 9

In 1994, Comet Shoemaker-Levy 9 slammed into Jupiter. The simulation sl9.gsim lets you watch the comet as it orbits Jupiter. A close pass to Jupiter in July 1992 causes the comet to break into pieces. In this simulation, Shoemaker-Levy 9 is represented by 20 test particles all orbiting Jupiter in SL9's orbit. The test particles occupy a sphere of space 10km in diameter. While far from Jupiter, the particles stay together, but after passing close to Jupiter, the planet's gravity scatters the particles. Over the next orbit, they spread out in their orbit to form a chain. Gravity alone can not explain the spacing observed in real life. Perhaps fresh outgassing after the comet was torn apart, exposing the interior of the comet, helped spread the pieces out even more.
After completing a full orbit, these cometary fragments strike Jupiter in June 1994. In real life, it took several days for all the particles to impact Jupiter. In this simulation, with the chain of particles more compact than what was observed, only 1/2 hour elapses between the first fragment strike and the last one.

Starting conditions for this simulation were obtained from JPL Horizons Ephemeris Computation Service.

Comet Shoemaker-Levy 9 has been orbiting Jupiter since the early 20th century, tracing a chaotic path.

Shoemaker-Levy 9 approaches Jupiter for the second to last time. In July 1992, a close pass to Jupiter will break the comet up into fragments.

Shoemaker-Levy 9 receeds from Jupiter after its July 1992 close approach. This broken comet will soon make a U-turn and head back to Jupiter for the final time.
The fragments slam into Jupiter's cloudtops in June 1994, causing explosions larger than Earth.